How Penguins' Shape-Shifting Huddle Keeps Them Warm

In the icy freeze of Antarctica, Emperor penguins huddle for
warmth – and they stay toasty even though they constantly rotate
positions in the scrum.

Now, researchers have modeled the workings of the huddle, looking
at the system through the lens of fluid dynamics.

Francois Blanchette, an applied mathematician at the University
of California, Merced, says that it took a bit of serendipity to
bring him into the topic.

"I was watching those penguin movies and got to thinking: I work
with similar things," Blanchette said.

"You can see the wind blowing in all these movies, and you can
see snowflakes — I thought maybe there's a way to get involved in
the idea of penguin huddling."

Biologists have long observed how hundreds of penguins gather
together in order to resist the Antarctic temperatures of -60 F
and gusts of 100 mph.

Other researchers showed that the penguins move from place to
place within the packed group, moving outside penguins to the
warmer spots and dispersing the heat loss.

Inside the huddle, temperatures have been known to reach 70
degrees F. Huddling is particularly important, as the penguins
don't eat for up to 115 days and need to conserve as much energy
as possible.

Blanchette took the idea a step further and created math models
of the shape and dynamics of the huddle. He found that when
penguins try to maximize their warmth — the coldest ones move to
the best available spot — and the huddle takes the form of a
cigar.

Blanchette soon realized that the oblong shape didn't match up
with what he saw in penguin movies, so he added another factor:
random heat loss to every penguin. That created a rounder huddle
with a smattering of holes in it, with a bit of elongation in the
direction of the wind.

The team was surprised to find that even though each penguin was
out to help itself, the cold ended up being shared nearly equally
over the whole group.

"If you wanted to design a process that's fair, this is a close
approximation," said Blanchette.

Barbara Wienecke, a biologist with the Australian Antarctic
Division who studies penguins, said the model was interesting.
She added that reality may be more complex than the model, which
assumes there are few gaps in the huddle, suggests.

"Huddles are highly dynamic and not as symmetrical as one might
expect," Wienecke said, who had a biological shape in mind for
the huddle. "The outline of a huddle can make it look more like
an ameoba than a circle so to a point openings often exist,
depending on the number of birds in a huddle."

Penguins huddles aren't the only shape-shifting animal grouping —
other biological masses have dynamics that can be modeled like
fluids, said Blanchette. He points to colonies of bacteria that
change shape in response to food or toxins.

In addition, the model could be programmed into robots who need
to swarm and huddle to survive.

"Imagine a group of robots caught in a sandstorm, and they might
want to rotate who is exposed," Blanchette said. A biology-based
model could prescribe behavior to maximize survival for a group
faced with a nasty environmental situation.